PolyD films, typically prepared by chemical vapor deposition (CVD), have received considerable attention in recent years, because of their remarkable properties. These include high thermal conductivity, optical transparency, high refractive index, mechanical hardness and chemical inertness.
It is known that the hardness of diamond is strongly dependent on crystal orientation, so that a soft diamond crystal plane can be abraded by a hard crystal plane. This fact is used in conventional diamond polishing, which involves removal of material from soft crystal planes by means of (randomly oriented) diamond powder.
PolyD film comprises many crystallites, and there will always be present crystallites that have one of their hard directions approximately oriented in the removal direction, and thus cannot be removed easily by conventional means. It is principally for this reason that removal of material from polyD films has been problematical.
Commonly assigned U.S. patent application Ser. No. 07/822,470, filed Jan. 17, 1992 now abandoned for J. E. Graebner et al., discloses a method of removing material from a polyD film that comprises maintaining the film in intimate contact with Fe, Ni, Mn or Ti at 600.degree.-1100.degree. C. See also S. Jin et al., Applied Physics Letters, Vol. 60, p. 1948 (1992), and S. Jin et al., Diamond Films and Related Materials, Vol. 1, p. 949 (1992). The required intimate contact typically is attained through application of pressure during the high temperature treatment. Commonly assigned U.S. patent application Ser. No. 07/908,130, filed Jul. 2, 1992 for W. C. Dautremont-Smith et al., discloses thinning of polyD film by contacting the film with molten or partially molten metal that dissolves carbon, exemplarily a rare earth (e.g., La or Ce) or mixture of rare earths. It also discloses that portions of a surface of the polyD film can be protected by masks against the liquid metal. See also commonly assigned U.S. patent application Ser. No. 07/955,634 now U.S. Pat. No. 5,328,550, filed Oct. 2, 1992 for J. E. Graebner et al., which discloses use of a molten or partially molten alloy of a rare earth metal (e.g., Cc) and a melting point-lowering metal, e.g., Ni, permitting a drastic reduction in thinning temperature, as compared to the method of the '130 application.
U.K. Patent application GB 2,061,904A discloses shaping a diamond body (not polyD) by contacting the body with an appropriately shaped metal (preferably Fe, Ni, Pt or alloys thereof) "template" at a temperature in the range 600.degree.-1800.degree. C. in vacuum, inert gas atmosphere, or in an atmosphere which does not react with diamond but reacts with carbon dissolved in the metal.
In view of the remarkable properties of diamond, it would be highly desirable to have available a technique for shaping polyD material into non-planar (e.g., lenticular) shape. Such a technique could, for instance, be used to produce optical elements (e.g., lenses, arrays of microlenses) or mechanical elements (e.g., wires, needles) from polyD material. This application discloses such a technique.